1. Field of the Invention
The invention relates to a method and arrangement for the regulation of the rail pressure in an internal combustion engine, wherein the rail pressure is regulated by way of a control unit.
2. Description of the Related Art
Various fuel injection systems are commonly used in internal combustion engines. Common rail fuel injection describes a fuel injection system wherein a high pressure pump brings fuel to a high pressure level. The fuel comes into a pipe system, known as the rail, where it is under pressure. The common rail system allows separation of the pressure generation from the actual injection process. The rail pressure is regulated by a pressure control valve or a suction throttle and is monitored by a rail pressure sensor. An automatic control is provided for this, wherein the target rail pressure is preset.
The internal combustion engine can basically be in a steady state operational state or a transient operational state. In the steady state operational state the rotational speed, as well as the rail pressure are already stable. In the transient operational state this is not the case. In order to reduce fluctuations of the target high pressure in the steady state operational state, a target high pressure filter having a long dwell time is required. In contrast, in the transient operation a target high pressure filter having a very short dwell time is required. In the prior art, a PT1-filter with a constant time constant was used. In order to enable a good steady state performance of the high pressure control circuit this time constant must be set very high. This had the disadvantage that the target high pressure is delayed too much during transient operations.